Narrative:

I was inbound to pia VOR on the 075 degree radial (headed wsw), at 6000 ft. Pia approach called out traffic northwest of my position 'sbound is an mdt.' I sighted the traffic and reported, 'traffic in sight.' pia approach replied, 'maintain visual separation, the aircraft at 8000 ft will be descending through your altitude.' the mdt called pia approach and said that he did 'not have the traffic (meaning me) in sight, but we've got him on TCASII.' if the courses of each aircraft would have remained constant, the mdt should have passed in front of me as it flew through my altitude. As the mdt neared my position, pia approach instructed the mdt to 'turn left heading 170 degrees.' the mdt complied and also responded that he still did not have me in visual contact. On this new heading, collision with the mdt was imminent. As I prepared to maneuver my aircraft, pia approach instructed the mdt to 'turn left heading 150 degrees for traffic.' the mdt complied and commented again that he still did not have me in sight. Our aircraft passed within 1 1/2 mi horizontally at equal altitudes. I was put in a situation where I was expected to avoid an aircraft that was much faster than me, within a few mi of my position, and maneuvering and descending upon me, all without having me in visual contact. Pia approach had given me the responsibility of maneuvering to avoid the descending mdt, but I was faced with not knowing how to maneuver considering the following 2 facts: 1) pia approach had begun to give the mdt vectors toward my aircraft, and I had no idea which way he was going to turn the mdt next. 2) the mdt had acknowledged that they were tracking my aircraft on TCASII, and I did not know if the mdt would begin evasive maneuvering due to TCASII commands, since we were in such close proximity. As a common practice, I have seen controllers ask pilots to maintain visual separation from other aircraft to allow a smoother or faster flow of traffic, especially when operating in a busy area. I do not know what the pia approach had in mind. Traffic did not seem to be especially busy at this time. It appears to me that the pia approach controller merely 'bailed out' of his responsibility to maintain separation between IFR traffic by instructing me to 'maintain visual separation,' then proceeding to recklessly descend the mdt. It also appears that he saw the conflict too late and tried to correct it when he told the mdt to 'turn left heading 150 degrees for traffic.' I believe it was a very dangerous situation that could have been avoided, had the controller handled it differently. Another 60 seconds for the mdt at 8000 ft would have certainly provided better separation. Waiting for one of the mdt crew to obtain visual contact of my aircraft would have been safer also. It was nearly impossible for me to maintain a safe separation between the 2 aircraft since the mdt was faster than me, descending, and not maintaining a constant heading. I thought the intentions of pia approach were for me to maintain separation with the mdt as he descended through my altitude sbound, but this evidently was not the case. I was unaware of the intentions of both the controller and the mdt.

Related reports:

Google
 

Original NASA ASRS Text

Title: ATC VECTORS AN ACR MDT INTO A CONFLICT WITH AN SMT.

Narrative: I WAS INBOUND TO PIA VOR ON THE 075 DEG RADIAL (HEADED WSW), AT 6000 FT. PIA APCH CALLED OUT TFC NW OF MY POS 'SBOUND IS AN MDT.' I SIGHTED THE TFC AND RPTED, 'TFC IN SIGHT.' PIA APCH REPLIED, 'MAINTAIN VISUAL SEPARATION, THE ACFT AT 8000 FT WILL BE DSNDING THROUGH YOUR ALT.' THE MDT CALLED PIA APCH AND SAID THAT HE DID 'NOT HAVE THE TFC (MEANING ME) IN SIGHT, BUT WE'VE GOT HIM ON TCASII.' IF THE COURSES OF EACH ACFT WOULD HAVE REMAINED CONSTANT, THE MDT SHOULD HAVE PASSED IN FRONT OF ME AS IT FLEW THROUGH MY ALT. AS THE MDT NEARED MY POS, PIA APCH INSTRUCTED THE MDT TO 'TURN L HDG 170 DEGS.' THE MDT COMPLIED AND ALSO RESPONDED THAT HE STILL DID NOT HAVE ME IN VISUAL CONTACT. ON THIS NEW HDG, COLLISION WITH THE MDT WAS IMMINENT. AS I PREPARED TO MANEUVER MY ACFT, PIA APCH INSTRUCTED THE MDT TO 'TURN L HDG 150 DEGS FOR TFC.' THE MDT COMPLIED AND COMMENTED AGAIN THAT HE STILL DID NOT HAVE ME IN SIGHT. OUR ACFT PASSED WITHIN 1 1/2 MI HORIZLY AT EQUAL ALTS. I WAS PUT IN A SIT WHERE I WAS EXPECTED TO AVOID AN ACFT THAT WAS MUCH FASTER THAN ME, WITHIN A FEW MI OF MY POS, AND MANEUVERING AND DSNDING UPON ME, ALL WITHOUT HAVING ME IN VISUAL CONTACT. PIA APCH HAD GIVEN ME THE RESPONSIBILITY OF MANEUVERING TO AVOID THE DSNDING MDT, BUT I WAS FACED WITH NOT KNOWING HOW TO MANEUVER CONSIDERING THE FOLLOWING 2 FACTS: 1) PIA APCH HAD BEGUN TO GIVE THE MDT VECTORS TOWARD MY ACFT, AND I HAD NO IDEA WHICH WAY HE WAS GOING TO TURN THE MDT NEXT. 2) THE MDT HAD ACKNOWLEDGED THAT THEY WERE TRACKING MY ACFT ON TCASII, AND I DID NOT KNOW IF THE MDT WOULD BEGIN EVASIVE MANEUVERING DUE TO TCASII COMMANDS, SINCE WE WERE IN SUCH CLOSE PROX. AS A COMMON PRACTICE, I HAVE SEEN CTLRS ASK PLTS TO MAINTAIN VISUAL SEPARATION FROM OTHER ACFT TO ALLOW A SMOOTHER OR FASTER FLOW OF TFC, ESPECIALLY WHEN OPERATING IN A BUSY AREA. I DO NOT KNOW WHAT THE PIA APCH HAD IN MIND. TFC DID NOT SEEM TO BE ESPECIALLY BUSY AT THIS TIME. IT APPEARS TO ME THAT THE PIA APCH CTLR MERELY 'BAILED OUT' OF HIS RESPONSIBILITY TO MAINTAIN SEPARATION BTWN IFR TFC BY INSTRUCTING ME TO 'MAINTAIN VISUAL SEPARATION,' THEN PROCEEDING TO RECKLESSLY DSND THE MDT. IT ALSO APPEARS THAT HE SAW THE CONFLICT TOO LATE AND TRIED TO CORRECT IT WHEN HE TOLD THE MDT TO 'TURN L HDG 150 DEGS FOR TFC.' I BELIEVE IT WAS A VERY DANGEROUS SIT THAT COULD HAVE BEEN AVOIDED, HAD THE CTLR HANDLED IT DIFFERENTLY. ANOTHER 60 SECONDS FOR THE MDT AT 8000 FT WOULD HAVE CERTAINLY PROVIDED BETTER SEPARATION. WAITING FOR ONE OF THE MDT CREW TO OBTAIN VISUAL CONTACT OF MY ACFT WOULD HAVE BEEN SAFER ALSO. IT WAS NEARLY IMPOSSIBLE FOR ME TO MAINTAIN A SAFE SEPARATION BTWN THE 2 ACFT SINCE THE MDT WAS FASTER THAN ME, DSNDING, AND NOT MAINTAINING A CONSTANT HDG. I THOUGHT THE INTENTIONS OF PIA APCH WERE FOR ME TO MAINTAIN SEPARATION WITH THE MDT AS HE DSNDED THROUGH MY ALT SBOUND, BUT THIS EVIDENTLY WAS NOT THE CASE. I WAS UNAWARE OF THE INTENTIONS OF BOTH THE CTLR AND THE MDT.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.